The invention relates to a swashplate pivot bearing of a hydraulic adjustment unit in an axial piston machine of the swashplate type. The invention relates particularly to swashplate pivot bearings having a timing/tracking mechanism.
The delivery capacity or absorption volume of adjustable axial piston machines of the swashplate type is adjusted via a pivotable swashplate in that the swashplate, which in the zero position of the axial piston machine stands perpendicularly to the axis of rotation of the axial piston machine, by being pivoted about a pivot axis perpendicularly to the axis of rotation of the axial piston machine, reduces or increases the volume of the individual cylinders arranged axially with respect to the drive/driven shaft. In this case, the pistons guided slidably on the swashplate, depending on the angular position with respect to their rotation about the axis of rotation of the drive/driven shaft of the axial piston machine, are pushed to a greater or lesser extent into the pressure cylinders of the cylinder block by the pivoted swashplate.
On account of the high forces which are to be supported and which emanate from the pressure cylinders, ring-segment rolling bearings are usually employed in this case as swashplate pivot bearings, preferably cylindrical rolling bodies being used. For this purpose, the swashplates are conventionally designed to be partly cylindrical on the side facing away from the pistons and cylinders. As a counterbearing, the housing for receiving the outer segment of the ring-segment rolling bearings is designed to be partly hollow-cylindrical in this region. When the axial piston machine is in operation, the swashplate pivot bearings are under high load and therefore have to be of robust design. Moreover, the swashplate pivot bearings should ensure uniform easy-running adjustment of the swashplate throughout the lifetime of the axial piston machine, without high frictional forces arising in the swashplate pivot bearing or the swashplate pivot bearing being subjected to premature wear, which may lead to the failure of the axial piston machine. Furthermore, high outlay in terms of the maintenance and/or repair of the swashplate pivot bearings is to be avoided.
A conventional swashplate pivot bearing is known, for example, from DE 10 2005 056 088 A1. According to this prior art, the swashplate is mounted in a roller bearing arrangement which has an inner segment, an outer segment and a cage for guiding a plurality of rollers which are arranged between the inner segment and the outer segment, the inner segment on the swashplate, the outer segment on the housing and the cage between the inner and the outer segment being designed in each case as partial circle segments. The rollers extend only over a circle segment predetermined by the cage and are moved back and forth during the pivoting movement of the swashplate.
In the swashplate pivot bearing described in DE 10 2005 056 088 A1, there is a timing/tracking mechanism which controls the movement of the cage with the effect of limited tracking of the movement of the swashplate. It is necessary for the cage to track the movement or adjustment of the swashplate in order to ensure a favorable rolling movement or roll-off movement of the rollers on the raceways for the rolling bodies on the inner and the outer segment. Since the two raceways, that on the outside of the inner segment and that on the inside of the outer segment, are arranged concentrically, preferably concentrically to the pivot axis of the pivot bearing, the radii of the raceways are different, and during the pivoting of the swashplate sliding or slipping of the rolling bodies occurs if these are not tracked in the circumferential direction in a correcting manner. Such tracking can be implemented, for example, with rolling bodies received in a cage, in that the cage is tracked in the circumferential direction. For this purpose, the arcuate displacement of the cage preferably amounts to half the arcuate displacement of the swashplate in the circumferential direction. Moreover, repeated pivoting/tilting of the swashplate may cause the rollers between the outer segment mounted on the housing and the swashplate to slip into positions other than into the desired optimal supporting positions for counteracting the axial pressure of the swashplate, if the rollers are not tracked. In order to implement this tracking, for example according to DE 10 2005 056 088 A1, a connecting member is provided, which is mounted rotatably on the outer segment and has a slot in which pins fastened to the inner segment and to the cage engage and are guided in such a way that the connecting member limits the arcuate movement of the cage. A similar arrangement with resilient elements for connecting the inner segment, cage and outer segment is known from DE 10 2006 023 711 A1.
According to DE 10 2005 023 275 A1, the tracking of the rollers during pivoting of the swashplate is brought about in that one or more of the rollers are equipped with a gearwheel meshing in each case with toothing on the swashplate and on the housing of the axial piston machine. A disadvantage of using gearwheels is that it is difficult to set the timing, and faulty setting may lead to failure of the bearing and therefore of the entire hydrostatic machine.
DE 10 2009 013 094 A1 describes a swashplate pivot bearing which is designed without a cage for the rollers. The tracking of the rollers or rolling bodies takes place here via a slotted-link control preferably arranged at both ends of the bearing region which the rollers brush over. The tracking device comprises limit stop elements for the rollers, which are moved jointly with the rollers by means of the slotted-link guide during a pivoting movement of the swashplate pivot bearing. One of the slotted links is fixed to a machine in a housing portion and the other moves together with the swashplate, with the result that the limit stop elements connected to the sliding block are displaced with the effect of the desired tracking.
The swashplate pivot bearing according to DE 10 2009 013 094 A1 has no inner segment, but instead the rollers run directly on the swashplate. This necessitates a high quality of the raceway of the rollers on the swashplate, along with a correspondingly high outlay in production terms. The form of construction according to DE 10 2005 056 088 A1 avoids this disadvantage by providing a separate inner segment and a separate outer segment as a raceway for the rollers, the said segments being mounted in each case on the swashplate or on the housing of the hydraulic adjustment unit. This avoids the need for special requirements to be met by the housing and swashplate which do not have to have hardened raceways for the rollers. To connect and adjust the outer segment and inner segment to and with respect to one another and to and with respect to the swashplate and housing, stamped noses are used. However, producing these noses by stamping is difficult and, because of their small size, presents assembly problems.